1. Field of the Invention
The present invention relates to an X-Y direction input device, and more particularly to an X-Y direction input device called a mouse (trade name).
2. Description of the Related Art
A computer system is basically made up of a display screen, a display controller, data, various input devices and so on.
There are known various forms of input devices up to now. As one of those input devices, an X-Y direction input device called a "mouse" (trade name) has been developed in which when a case is moved on a base in any desired direction, the direction and amount of movement of the case is detected.
Such an X-Y direction input device is basically made up of a rotated spherical body (referred to simply as a spherical body hereinafter) formed of a steel ball, for example, a first driven roller contacting the spherical body to be rotatable by rotating force of the spherical body, a second driven roller contacting the spherical body to be rotatable by rotating force of the spherical body and having an axis substantially perpendicular to the axis of the first driven roller, first and second rotational amount detecting means formed by rotary electrical parts, such as variable resistors or encoders, for individually detecting respective amounts of rotation of the first and second driven rollers, and a case for housing the spherical body, the first and second driven rollers, and the first and second rotational amount detecting means.
An opening is formed in a lower wall of the case so that part of the spherical body projects downward through the opening. When an operator holds the case by the hand and rolls it on a predetermined base in any desired direction, the first and second driven rollers rotate respectively in the predetermined directions. The first and second rotational amount detecting means take out the directions and amounts of rotation of the driven rollers in the form of voltage or digital signals indicating components of the rotation in the X-axis and Y-axis directions. These signals are input to a display device of the computer system.
In the X-Y direction input device thus constructed, frictional force applying means is required to resiliently urge the spherical body toward the first driven roller and the second driven roller under even forces for applying frictional forces between the spherical body and both the driven rollers.
A typical example of conventional frictional force applying means will be described with reference to FIGS. 13 and 14.
The conventional frictional force applying means comprises a rolling contact roller 57' of synthetic resin, a roller support member 58' for supporting the rolling contact roller 57', a container 17' for supporting the roller support member 58', and a coil spring 59'.
The roller support member 58' formed of a molding of synthetic resin has a pair of rotary support shafts 58'a provided on its upper side walls, and a spring receiving projection 58'b (see FIG. 14) provided on its lower back surface. Further, a bearing portion 58'c is formed to be open forward in a middle position between the rotary support shafts 58'a and the spring receiving projection 58'b. Both ends of a support shaft 60' inserted through the rolling contact roller 57' is press-fitted to the bearing portion 58'c so that the rolling contact roller 57' is rotatably supported by the roller support member 58' with the support shaft 60' serving as a rotary shaft.
The roller support member 58' thus constructed is inserted into an open room 17'a of the container 17' in such a state that the coil spring 59' is fitted at its one end over the spring receiving projection 58'b. With the insertion of the roller support member 58', as shown in FIG. 14, the rotary support shafts 58'a of the roller support member 58' enter cutout portions 17'b in opposite walls of the container 17', whereby the coil spring 59' is held in a compressed state between the roller support member 58' and an inner wall of the container 17'. The resulting resilient force of the coil spring 59' urges the roller support member 58' to rotate clockwise, as viewed on the drawing, about the rotary support shafts 58'a as fulcra. By virtue of the biasing force, part of the rolling contact roller 57' supported by the roller support member 58' slightly projects out of the container 17' toward the opening where the spherical body is placed, and an outer wall of the roller support member 58' comes into abutment with an inner wall of the container 17'. The roller support member 58' and the rolling contact roller 57' are thereby prevented from displacing.
With the above conventional structure, the spherical body can be pressed upon both the driven rollers under even forces by arranging the rolling contact roller and the coil spring on a straight line connecting a point where the axes of the first and second driven rollers cross each other and the center of the spherical body.
The conventional frictional force applying means, however, requires a large number of parts and is costly because it is made up of four independent components; i.e., the rolling contact roller 57' of synthetic resin, the roller support member 58' for supporting the rolling contact roller 57', the container 17' for supporting the roller support member 58', and the coil spring 59'. Another problem is that the roller support member 58' is less cost effective in manufacture and machining because of its complicated configuration.